The present invention relates to a water closet flushing apparatus and more particularly, to a water closet flushing apparatus which can supply a predetermined quantity of water irrespective of fluctuations in the supply pressure of the flushing water.
Water closets of the flushing type are provided with a bowl portion having a bowl shape and in which excreta is received and held, and a trap discharge passage having the shape of an inverted letter "U" and which communicates with a bottom portion of this bowl portion.
The quantity of flushing water that is supplied to the water closet must be a quantity that can clean the bowl portion and that can also generate a syphon action in the trap discharge path and thus completely discharge the water containing excreta. The value for this quantity of water is predetermined by the shape and size of the water closet, and its purpose of use.
In conventional flushing apparatus, there is known a type where an automatic opening and closing valve apparatus is used as the means to control the quantity of flushing water supplied. In this case, the water supply pressure of the flushing water is assumed to be constant, and the valve opens and closes for a predetermined time to supply the flushing water.
However, the water supply pressure of the flushing water often varies due to factors such as the location where the water closet is installed and the time that the water closet is used, and it is not possible to ensure a predetermined quantity of water by simply controlling the time for which the valve is open. Because of this, the general method involves holding the valve open for a longer time than is necessary, and supplying a quantity of flushing water that is greater than a predetermined quantity. Another method that can be thought of involves setting the water supply pressure to a high pressure beforehand but doing this involves the supply of a larger quantity of flushing water than is necessary, and therefore flushing water is also wasted with this method. In addition, when the supply water pressure becomes high, there is also the problem of the flushing water splashing to outside of the bowl when the water closet is flushed.
Because of this, development is being performed for a water closet flushing apparatus that performs the opening and closing control of an automatic opening and closing valve by providing a flow meter along a water supply pipe and measuring the quantity of flushing water supplied (such as for example, Japanese Patent Laid-Open Publication No. 114734/1988).
However, in the case where a flow meter is used, it is necessary to have a large installation shape since the flow meter itself is large. In addition, there is a large water pressure loss because of the need to drive a gear mechanism for the flow meter calculations and in particular, in the case where there is a low water supply pressure, this influence of the pressure loss creates the problem of difficulty in performing accurate flow quantity control. In addition, the flow quantity control meter uses a gear mechanism and so the response is slow and it is not possible to accurately detect the flow quantity when flushing water supply commences and when there are instantaneous changes in the flow. Furthermore, in order for the flow meter to detect the actual quantity of water that is flowing, the flow meter is disposed on the upstream side of the opening and closing valve and when the water is cut off, does not function to predict abnormalities in the water supply system beforehand.
In addition, recently, for the purposes of reducing the amount of flushing water that is supplied to the water closet and to definitely generate the syphon action necessary in the trap discharge passage to perform flushing, there has been used a method in which separate water supply systems are used to supply flushing water to the bowl portion and the trap discharge passage (such as for example, Japanese Patent Laid-Open Publication No. 30092/1980). In this case as well, it is necessary to supply predetermined amounts of flushing water to the water supply passages of the separate systems but if there is a fluctuation in the water supply pressure, then for the same reason as has already been described, there is the problem of the optimum flushing effect not being attained.